Turn off Automatic finger Curling in Rigify
I realised somehow the fingers were set to tentacle. I just now learned the workflow of setting the rig type in the metarig at the base of each chain.
Setting the rigify type to basic.copy_Chain get me the plain FK finger setup I was looking for.
The problem illustrated above is a feature of the tentacle chain which is what it was set to. The tentacle chain uses rotation constraints to automatically rotate every bone according to its parents rotation. you can simply disable the constraint for every bone if you want to use a tentacle chain without the automatic curling.